Diamond-based composite wave-absorbing material

Abstract

The embodiment of the application discloses diamond-based composite wave-absorbing material; the method comprises the following steps: S1, the surface of nano-diamond particles is graphitized to obtain graphitized diamond composite particles; S2, the graphitized diamond composite particles are formed by molding to obtain a diamond-based composite wave-absorbing material blank; S3, the diamond-based composite wave-absorbing material blank is treated by high temperature and high pressure to obtain the diamond-based composite wave-absorbing material; the diamond-based composite wave-absorbing material has a minimum reflection loss value of -61.47 dB at 5.5 mm, the widest effective absorption bandwidth can reach 4.0 GHz at 2.7 mm, the Vickers hardness is between 40 and 60 GPa, the material is superhard, the normal temperature thermal conductivity is between 3.4 and 3.7 W / m*K, the initial oxidation temperature is between 1100 and 1250 DEG C, the corrosion current density is between 10 ‑6 ~10 ‑7 A / cm 2 , the self-corrosion potential is between -200 and 0 mV, the corrosion rate is between 0.001 and 0.005 mm / a, and the material is very corrosion resistant.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials technology, specifically relating to diamond-based composite microwave absorbing materials. Background Technology

[0002] Electromagnetic absorbing materials that can resist and weaken electromagnetic radiation have become a research hotspot in the field of materials science.

[0003] The role of microwave absorbing materials in stealth technology is becoming increasingly important. Traditional metallic magnetic microwave absorbing materials, while possessing microwave absorbing properties, suffer from drawbacks such as large mass, poor thermal shielding performance, and poor corrosion resistance. Carbon-based microwave absorbing materials and their composites with magnetic metallic microwave absorbing materials can effectively avoid these drawbacks, but they have disadvantages such as poor hardness and poor thermal stability. Conductive polymer microwave absorbing materials have poor environmental stability and weak mechanical properties, making them unsuitable for harsh environments, especially for long-term use or exposure. Ceramic microwave absorbing materials, while possessing good thermal stability, also suffer from drawbacks such as large mass and relatively weak microwave absorbing performance.

[0004] Carbon-based materials with different structural morphologies can be constructed using different preparation methods to improve the wave absorption performance of wave-absorbing materials. It is hoped that carbon-based wave-absorbing materials with stable wave absorption performance in harsh environments can be obtained, meeting the needs of the aerospace and deep-sea fields for wave-absorbing materials that are lightweight, have good thermal shielding performance, good corrosion resistance, excellent wave absorption performance, and excellent mechanical and thermal stability. Summary of the Invention

[0005] In view of this, some embodiments disclose diamond-based composite microwave absorbing materials, which are obtained by a method for preparing diamond-based composite microwave absorbing materials. The diamond-based composite microwave absorbing materials are prepared from graphitized diamond composite particles, which are composed of a diamond matrix and a graphene layer on the surface of the diamond matrix. The effective absorption bandwidth of the diamond-based composite microwave absorbing materials is between 2.6 and 4 GHz, and the lowest reflection loss value is between -30 and -61.47 dB. The effective absorption frequency of the diamond-based composite microwave absorbing materials with a thickness between 1.5 and 5.5 mm is between 4.28 and 18 GHz.

[0006] The Vickers hardness of diamond-based composite microwave absorbing materials ranges from 40 to 60 GPa, the thermal conductivity at room temperature ranges from 3.4 to 3.7 W / m·K, and the corrosion current density is between 10 GPa and 10 GPa. -6 ~10 -7 A / cm 2 The self-corrosion potential is between -200 and 0 mV, and the initial oxidation temperature is between 1100 and 1250 °C.

[0007] Furthermore, some embodiments disclose a method for preparing diamond-based composite microwave absorbing materials, including the following steps:

[0008] S1. The surface of nanodiamond particles is graphitized to obtain graphitized diamond composite particles.

[0009] S2. Graphitized diamond composite particles are molded to obtain a diamond-based composite microwave absorbing material blank;

[0010] S3. Diamond-based composite microwave absorbing material blanks are subjected to high temperature and high pressure treatment to obtain diamond-based composite microwave absorbing materials.

[0011] Furthermore, some embodiments of the diamond-based composite microwave absorbing material preparation method further include the following steps:

[0012] S4. Treat diamond-based composite microwave absorbing materials with acid solutions.

[0013] The diamond-based composite microwave absorbing material disclosed in this invention is prepared from graphitized diamond composite particles. Amorphous carbon on the surface of the diamond particles is graphitized to obtain diamond-based composite particles. These particles are then subjected to high-temperature and high-pressure treatment to obtain a diamond-based composite microwave absorbing material with excellent microwave absorption performance. At a thickness of 5.5 mm, the minimum reflection loss reaches -61.47 dB, and at 2.7 mm, the effective absorption bandwidth can reach up to 4.0 GHz. The sample also possesses excellent mechanical properties, thermal shielding performance, corrosion resistance, and thermal stability. Its Vickers hardness is between 40 and 60 GPa, classifying it as an ultrahard material. Its room-temperature thermal conductivity is between 3.4 and 3.7 W / m·K, its initial oxidation temperature is between 1100 and 1250 °C, and its corrosion current density is between 10... -6 ~10 -7 A / cm 2 With a self-corrosion potential between -200 and 0 mV and a corrosion rate between 0.001 and 0.005 mm / a, it is a highly corrosion-resistant material and has good application prospects in aerospace and deep-sea fields. Attached Figure Description

[0014] Figure 1 Photograph of the diamond-based composite microwave absorbing material sample disclosed in Example 1;

[0015] Figure 2 The image shows the microwave absorption performance of the diamond-based composite microwave absorbing material sample disclosed in Example 1.

[0016] Figure 3 The image shows the microwave absorption performance of the diamond-based composite microwave absorbing material sample disclosed in Example 2.

[0017] Figure 4 The image shows the microwave absorption performance of the diamond-based composite microwave absorbing material sample disclosed in Example 3.

[0018] Figure 5 This is a three-dimensional image of the microwave absorption performance of the diamond-based composite microwave absorbing material sample disclosed in Example 3;

[0019] Figure 6 TEM image of the diamond-based composite microwave absorbing material sample disclosed in Example 3;

[0020] Figure 7 This is a comprehensive comparison chart of multiple properties of the diamond-based composite microwave absorbing material samples disclosed in Examples 1-3 with other microwave absorbing materials. Detailed Implementation

[0021] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in these embodiments of the invention, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in these embodiments is merely for describing particular implementations and is not intended to limit the scope of the disclosure of these embodiments.

[0022] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this invention pertain; other experimental methods and technical means not specifically noted in the embodiments of this invention refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0023] The terms “basic” and “approximately” used in this document are to describe small fluctuations. For example, they can mean less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Numerical data presented or expressed in range format in this document are used for convenience and brevity only, and should therefore be flexibly interpreted to include not only the explicitly listed values ​​that define the range, but also all independent values ​​or subranges contained within that range. For example, a numerical range of “1–5%” should be interpreted to include not only the explicitly listed values ​​from 1% to 5%, but also the independent values ​​and subranges within the indicated range. Thus, this numerical range includes independent values ​​such as 2%, 3.5%, and 4%, and subranges such as 1%–3%, 2%–4%, and 3%–5%, etc. This principle also applies to ranges that list only one value. Furthermore, this interpretation applies regardless of the width of the range or the characteristics described.

[0024] In this document, including in the claims, conjunctions such as "comprising," "including," "with," "having," "containing," "involving," and "accommodating" are understood to be open-ended, meaning "including but not limited to." Only the conjunctions "consisting of" and "composed of" are closed conjunctions.

[0025] To better illustrate the content of this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that the invention can be practiced even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail, in order to highlight the main points of the invention.

[0026] Without conflict, the technical features disclosed in the embodiments of the present invention can be combined arbitrarily, and the resulting technical solutions belong to the content disclosed in the embodiments of the present invention.

[0027] In some embodiments, the preparation method of diamond-based composite microwave absorbing material includes the following steps:

[0028] S1. The surface of nanodiamond particles is graphitized to obtain graphitized diamond composite particles. Typically, the surface of nanodiamond particles contains a certain amount of amorphous carbon. During the graphitization process, some of the amorphous carbon is oxidized and disappears. The remaining amorphous carbon undergoes graphitization transformation at high temperature, transforming into a graphite layer, i.e., a few layers of graphene are covered on the surface of the diamond matrix. Diamond matrix particles covered with a few layers of graphene are graphitized diamond composite particles.

[0029] In some embodiments, the graphitization treatment of the nanodiamond particles includes:

[0030] S101. Heat-treat the nanodiamond particles at 450-550°C in an air atmosphere; as an optional embodiment, the air atmosphere is flowing air with a flow rate set to 10-30 Sccm.

[0031] S102. The heat-treated nanodiamond particles are subjected to vacuum heat treatment at 1000-1200℃ to obtain graphitized nanodiamond composite particles.

[0032] S2. Graphitized diamond composite particles are molded to obtain a diamond-based composite microwave absorbing material blank. Typically, during the molding process, the graphitized diamond composite particles are tightly interlocked and stacked to form a diamond-based composite microwave absorbing material blank with a set shape.

[0033] S3. Diamond-based composite microwave absorbing material preforms are subjected to high-temperature and high-pressure treatment to obtain diamond-based composite microwave absorbing materials. Typically, during the high-temperature and high-pressure treatment of the diamond-based composite microwave absorbing material preforms, the graphitized diamond composite particles further intercalate, and the graphene layers distributed on the surface of the diamond matrix particles intercalate and fuse, forming interwoven graphene layers. These interwoven graphene layers possess excellent electrical conductivity, generating electrical losses, thus exhibiting excellent microwave absorption performance. Based on the excellent physicochemical properties of the diamond matrix and the good electrical conductivity of the graphene layers in the diamond-based composite microwave absorbing material, the diamond-based composite microwave absorbing material not only possesses excellent microwave absorption performance but also excellent mechanical properties, thermal properties, and corrosion resistance, exhibiting good comprehensive performance even in harsh environments. Typically, the pressed diamond-based composite microwave absorbing material blank is placed inside the cylindrical cavity of a pressing mold, allowing the blank to fill the interior of the cylinder. It is then subjected to high-temperature and high-pressure treatment in a six-sided press. After treatment under the set temperature and pressure conditions, the press is depressurized, and the diamond-based composite microwave absorbing material encased in the pressing mold is removed. The pressing mold used in the six-sided press is typically a combination of a zirconium cup and a molybdenum cup.

[0034] In some embodiments, the temperature for high-temperature and high-pressure treatment of the diamond-based composite microwave absorbing material blank is set to 1100–1300°C, and the pressure is set to 7–9 GPa.

[0035] The method for preparing diamond-based composite microwave absorbing materials disclosed in some embodiments further includes the following steps:

[0036] S4. Treat diamond-based composite microwave absorbing materials with acid solutions. Typically, the prepared diamond-based composite microwave absorbing material is encased in a pressing mold, which needs to be dissolved and removed using acid treatment.

[0037] In some embodiments, the acid solution is a mixed solution of sulfuric acid and nitric acid, wherein the molar ratio of sulfuric acid to nitric acid is 1:1 to 4.

[0038] In some embodiments, the diamond-based composite microwave absorbing material is boiled in an acid solution at a temperature of 150–210°C for 2–4 hours.

[0039] Some embodiments disclose diamond-based composite microwave absorbing materials, obtained by a method for preparing diamond-based composite microwave absorbing materials. The diamond-based composite microwave absorbing materials are prepared from graphitized diamond composite particles, which consist of a diamond matrix and a graphene layer on the surface of the diamond matrix. The effective absorption bandwidth of the diamond-based composite microwave absorbing materials is between 2.6 and 4 GHz, and the lowest reflection loss value is between -30 and -61.47 dB. The effective absorption frequency of the diamond-based composite microwave absorbing materials with a thickness between 1.5 and 5.5 mm is between 4.28 and 18 GHz. The Vickers hardness of the diamond-based composite material is between 40 and 60 GPa, the room temperature thermal conductivity is between 3.4 and 3.7 W / m·K, and the corrosion current density is between 10... -6 ~10 - 7 A / cm 2 The self-corrosion potential is between -200 and 0 mV, and the initial oxidation temperature is between 1100 and 1250 °C.

[0040] The technical details are further illustrated below with reference to the embodiments.

[0041] Example 1

[0042] The method for preparing the diamond-based composite microwave absorbing material disclosed in Example 1 includes:

[0043] S1. Ordinary nanodiamonds are placed in a tube furnace and heat-treated in an air atmosphere at 450°C for 60 minutes. Some amorphous carbon on the surface is oxidized and disappears. Then, the air atmosphere in the tube furnace is replaced with a vacuum environment and vacuum heat-treated at 1200°C to graphitize the surface and obtain graphitized nanodiamond composite particles.

[0044] S2. Pour the graphitized nanodiamond composite particles into a mold and use a cold press to compress the graphitized nanodiamond composite particles into a cylindrical sample with a diameter of 15.1 mm and a height of 4.7 mm. Then place the cylindrical sample into a cylindrical cavity made of zirconium cup and molybdenum cup to fully fill the cylindrical cavity.

[0045] S3. Use a six-sided press to treat the cylindrical sample under high temperature and high pressure. Set the pressure and power of the six-sided press to 70MPa and 8.2kW (7GPa, 1100℃). After the six-sided press is depressurized, take out the cylindrical sample.

[0046] S4. The hot-pressed cylindrical sample is placed in a prepared mixed solution of sulfuric acid and nitric acid for acid boiling at a temperature of 210°C for 4 hours to obtain a diamond-based composite microwave absorbing material sample.

[0047] Figure 1The image shows a sample of the diamond-based composite microwave absorbing material disclosed in Example 1. The diamond-based composite microwave absorbing material is prepared from graphitized diamond composite particles, which consist of a diamond matrix and a graphene layer covering the surface of the diamond matrix. The material contains disordered few-layer graphene embedded between nano-diamond matrices.

[0048] The diamond-based composite microwave absorbing material sample prepared in Example 1 was subjected to microwave absorption testing using the coaxial method. The reflection loss values ​​of the samples with different thicknesses were measured. Figure 2 As shown, the minimum reflection loss of the sample reaches -63.57dB when the thickness is 9mm, and the maximum effective absorption bandwidth is 2.6GHz when the thickness is 6mm.

[0049] Example 2

[0050] The preparation method of the diamond-based composite microwave absorbing material disclosed in Example 2 is the same as that in Example 1; wherein, in step S2, the pressure and power of the press are set to 70MPa and 8.3kW (7GPa, 1200℃).

[0051] The diamond-based composite microwave absorbing material sample prepared in Example 2 was subjected to microwave absorption testing using the coaxial method. The reflection loss values ​​of the samples with different thicknesses were measured. Figure 3 As shown, the minimum reflection loss of the sample reaches -28.93dB when the thickness is 2.6mm, and the maximum effective absorption bandwidth is 3.5GHz when the thickness is 2.9mm.

[0052] Example 3

[0053] The preparation method of the diamond-based composite microwave absorbing material disclosed in Example 3 is the same as that in Example 1; wherein, in step S2, the pressure and power of the press are set to 70MPa and 8.4kW (7GPa, 1300℃).

[0054] The diamond-based composite microwave absorbing material sample prepared in Example 3 was subjected to microwave absorption testing using the coaxial method. The reflection loss values ​​of the samples with different thicknesses were measured, such as... Figure 4 and Figure 5 As shown, the minimum reflection loss of the sample reaches -61.47dB when the thickness is 5.5mm, and the maximum effective absorption bandwidth is 4.0GHz when the thickness is 2.7mm. Figure 6 This is a TEM image of the diamond-based composite microwave absorbing material disclosed in Example 3.

[0055] In this embodiment, the coaxial method was used to test the sample with a vector network analyzer (Agilent E5071C). The outer diameter of the coaxial ring sample was 7 mm and the inner diameter was 3.07 mm. The test range was 1 to 18 GHz. The data was processed using Python software to calculate the reflection loss value.

[0056] Figure 7 This is a comparative graph showing the combined properties of the diamond-based composite microwave absorbing materials disclosed in Examples 1-3 with other samples. Compared with existing microwave absorbing materials, such as carbon nanotube composites, reduced graphene oxide composites, onion carbon, ceramic composites, and carbon fiber composites, the diamond-based composite microwave absorbing materials disclosed in Examples 1-3 exhibit higher levels of mechanical properties, thermal stability, thermal shielding performance, and corrosion resistance. Their Vickers hardness is between 40 and 60 GPa, classifying them as superhard materials. Their room-temperature thermal conductivity is between 3.4 and 3.7 W / m·K, their initial oxidation temperature is between 1100 and 1250 °C, and their corrosion current density is between 10... -6 ~10 -7 A / cm 2 The self-corrosion potential is between -200 and 0 mV, and the corrosion rate is between 0.001 and 0.005 mm / a, which means it is a very corrosion-resistant material.

[0057] The method for preparing diamond-based composite microwave absorbing material disclosed in this invention involves graphitizing amorphous carbon on the surface of diamond particles to obtain diamond-based composite particles. The diamond-based composite particles are then subjected to high-temperature and high-pressure treatment to obtain a diamond-based composite microwave absorbing material with excellent microwave absorption performance, which has good application prospects in aerospace and deep-sea fields.

[0058] The technical solutions and technical details disclosed in the embodiments of this invention are merely illustrative of the inventive concept of this invention and do not constitute a limitation on the technical solutions of the embodiments of this invention. Any conventional changes, substitutions, or combinations made to the technical details disclosed in the embodiments of this invention have the same inventive concept as this invention and are within the protection scope of the claims of this invention.

Claims

1. A diamond-based composite microwave absorbing material, characterized in that, The diamond-based composite microwave absorbing material is prepared from graphitized diamond composite particles, which are composed of a diamond matrix and a graphene layer on the surface of the diamond matrix. The diamond-based composite microwave absorbing material has an effective absorption bandwidth between 2.6 and 4 GHz, and a minimum reflection loss value between -30 and -61.47 dB. The effective absorption frequency of the diamond-based composite microwave absorbing material with a thickness between 1.5 and 5.5 mm is between 4.28 and 18 GHz. The Vickers hardness of the diamond-based composite material is between 40 and 60 GPa, the room-temperature thermal conductivity is between 3.4 and 3.7 W / m•K, and the corrosion current density is between 10... -6 ~10 -7 A / cm 2 The self-corrosion potential is between -200 and 0 mV, and the initial oxidation temperature is between 1100 and 1250 °C. The preparation method of the diamond-based composite microwave absorbing material includes the following steps: S1. The surface of the nanodiamond particles is graphitized to obtain graphitized diamond composite particles; specifically including: S101. The nanodiamond particles are heat-treated at 450-550℃ in an air atmosphere; S102. The heat-treated nanodiamond particles are vacuum heat-treated at 1000-1200℃ to obtain graphitized nanodiamond composite particles; wherein, the air atmosphere is flowing air with a flow rate set to 10-30 sccm. S2. Graphitized diamond composite particles are molded to obtain a diamond-based composite microwave absorbing material blank; S3. The diamond-based composite microwave absorbing material blank is subjected to high temperature and high pressure treatment to obtain the diamond-based composite microwave absorbing material; wherein, the temperature of the diamond-based composite microwave absorbing material blank is set to 1100~1300℃ and the pressure is set to 7~9GPa. S4. Treat the diamond-based composite microwave absorbing material with acid solution; the acid solution is a mixed solution of sulfuric acid and nitric acid, wherein the molar ratio of sulfuric acid to nitric acid is 1:1 to 4; the diamond-based composite microwave absorbing material is boiled in the acid solution at a temperature of 150 to 210°C for 2 to 4 hours.

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